The six-story, 44-foot-wide home at 50 East 69th Street clocks in at a whopping 21,070 square feet. Known as the Dommerich Mansion, it was built for international cotton magnate Otto Louis Dommerich in 1917 and was last used as a medical facility for expensive cosmetic surgery procedures.

Architect Henry C. Pelton, who designed Riverside Church, designed the neo-French classic-style building. It has 14 marble fireplaces, a basement with 15-foot ceilings, two elevators and a curved staircase that leads up to a stained glass dome.

It also has 3,350 square feet of outdoor space and terraces on the second floor and roof.

In other billionaire private-equity news, Howard Lutnick recently bought the massive triplex at the Pierre Hotel for $44 million – $80 million off its asking price.[NYP] – Rich Bockmann